Such a valve arrangement is used in many cases to actuate hydraulic drives in a working machine, a vehicle or another arrangement. For example in a backhoe, a first hydraulic drive can be used to tilt a beam in relation to a chassis, a second hydraulic drive can be used to tilt an arm in relation to the beam and a third hydraulic drive can be used to activate a shovel. A fourth hydraulic drive can be provided to turn the upper vehicle body in relation to the lower vehicle body.
In this connection, the use of a compensation arrangement has the advantage that a load-pressure independent control is obtained. The compensation arrangement ensures that a pressure drop over the directional valve arrangement or over a measuring orifice combined with the directional valve arrangement remains constant, independently of the intensity of the working pressure and independently of the opening degree of the directional valve arrangement. Thus, the flow of the hydraulic fluid from the supply channel arrangement to the connected hydraulic drive basically only depends on the opening degree of the directional valve arrangement. Thus, a practically proportional function of the directional valve arrangement is obtained.
In principle, there are two different ways of designing a compensation arrangement. A first compensation arrangement, in the following called “pre-compensation arrangement”, has a compensation valve that is flow-technically located upstream of the measuring orifice mentioned above. The compensation device has a throttle slide that is acted upon in the closing direction by the pressure upstream of the measuring orifice and in the opening direction by the pressure downstream of the measuring orifice, that is, by the load pressure plus the pressure of a spring. Such a compensation arrangement is occasionally also called a “primary individual compensation valve”.
Another embodiment, in the following called “post-compensation arrangement, uses a compensation valve that is connected in the flow direction downstream of the measuring orifice. The throttle slide in the downstream located compensation valve is acted upon in the opening direction of the pressure down-stream of the measuring orifice and in the closing direction by the highest load pressure and a spring.
With a valve module with post-compensation arrangement a parallel activation of two or more valve modules and an insufficient supply of hydraulic fluid will cause a uniform reduced fluid flow via all measuring orifices. The available fluid flow will thus be distributed proportionally to all drives. This is not possible with a valve module with a pre-compensation arrangement.